Fix for resource deletion after tracer provider shutdown

[lalitb]

Fixes #904

Changes

Change in the order of declarations of tracer-context, instrumentation library, resources, and processor to ensure that resources and instrumentation library objects are destroyed after processor.
Adding test-case is a bit tricky ( would be doing it before merging the PR): but this is the batch-processor example output when tracer provider is deleted ( before and after changes):

Before change:

Shutting down and draining queue....
{
  name          : Span 1
  trace_id      : 738d6e1ac63df645a59696e9e8b3bc7b
  span_id       : 2bb3160e4738beae
  tracestate    :
  parent_span_id: 0000000000000000
  start         : 1626709154132876300
  duration      : 1700
  description   :
  span kind     : Internal
  status        : Unset
  attributes    :
  events        :
  links         :
  resources     :
  instr-lib     : �"VُY7�`Y"V`0"V."V."VA0@"V�"V>"V>"VA]�f(JY¤C�`Y"V`0"V."VSY;��`?"V�Span 1?"V?"V�?(4"V05"VA�"Vp+"VA�>"]�5�@'@'?ײE
�`Y"V`0"V."VTY;�@"V�Span A"VHA"V�?(4"V05"VA�p@"]�$Xj[W=}4N�`Y"V`0"V."V'UY;�� B"V�Span 3HB"V

After change:

Shutting down and draining queue....
{
  name          : Span 10
  trace_id      : faa0a602c715e0019e0c9da8cac147bc
  span_id       : 18cd2ae1bc8d2724
  tracestate    :
  parent_span_id: 0000000000000000
  start         : 1626708952913928200
  duration      : 1600
  description   :
  span kind     : Internal
  status        : Unset
  attributes    :
  events        :
  links         :
  resources     :
        service.name: unknown_service
        telemetry.sdk.version: 1.0.0-rc3
        telemetry.sdk.name: opentelemetry
        version: 1
        telemetry.sdk.language: cpp
        service: test_service
  instr-lib     : foo_library
}

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #911 (788076d) into main (afcb08e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #911   +/-   ##
=======================================
  Coverage   95.44%   95.44%           
=======================================
  Files         158      158           
  Lines        6749     6749           
=======================================
  Hits         6441     6441           
  Misses        308      308           

Impacted Files	Coverage Δ
sdk/include/opentelemetry/sdk/trace/tracer.h	100.00% <ø> (ø)
sdk/src/trace/tracer.cc	87.50% <100.00%> (ø)
sdk/src/trace/tracer_context.cc	81.82% <100.00%> (ø)

[seemk]

Stumbled upon this, tested this PR and can confirm this fixes the use after free.

Thanks!

[lalitb]

@open-telemetry/cpp-approvers need help reviewing this. Its small change to reorder declaration for the fix.